1. Field of the Invention
The present disclosure relates to a method and apparatus for determining a Transport Block Size (TBS) in a wireless communication system, and more particularly, to a method and apparatus for determining a TBS table in association with 256 QAM.
2. Description of the Prior Art
Information may be transmitted through a signal using signal properties such as intensities, displacements, frequencies, and phases thereof. Modulation is a process of transforming such signal properties into proper waveforms according to a channel characteristic of a transmission medium. Also, a digital signal may be used to transmit digital information by mapping the digital information to one of bit stream and a digitalized analog signal (sampled or analog-to-digital converted signal). Digital modulation is a process of transforming such digital signal (e.g., digital symbol sequences) to a proper signal according to the channel characteristics of a transmission medium. As a representative digital modulation method having good bandwidth efficiency, an M-ary QAM modulation method is used. The M-ary QAM modulation method may be expressed as 2M QAM and the M-ary QAM modulation method includes QPSK (or 4QAM), 16QAM and 64QAM.
Various modulation methods are used for downlink (DL) data transmission in a wireless communication system such as Long Term Evolution (LTE) or LTE-Advanced. Such modulation methods include QPSK, 16QAM and 64QAM. By using these modulation methods, a Base Station (BS) transmits data to a User Equipment (UE), and the UE demodulates the transmitted signal and receives the data.
Recently, an amount of data transmitted and received between terminals and associated base stations have been increased abruptly due to sharp increase in the number of user terminals and in the data usage. This requires a modulation method that can rapidly process a large amount of data traffic.
Meanwhile, a BS selects one of the modulation methods based on a DL channel status, and notifies the UE of the selected modulation method by using DCI. The UE may identify the selected modulation method based on the received DCI and may receive the data through demodulation appropriate for the data modulation method.
When the base station transmits data to the User Equipment, the base station selects the modulation scheme based on the downlink channel state, and determines a Transport Block Size (TBS) using the selected modulation scheme. The TBS is required to determine an amount of data to be included in a single transport block when the base station transmits data to the User Equipment.
To this end, the User Equipment measures the downlink channel state, and transmits information associated with the measured channel state to the base station. In addition, the base station determines MCS index information mapped to each of QPSK, 16QAM, and 64QAM based on the information associated with the channel state, and determines the TBS.
However, a new modulation scheme is required due to the increase in data traffic and speed, and a method of determining a TBS in association with the new modulation scheme is required.